1. Field of the Invention
This invention relates to attenuators which are particularly adapted for the absorption of energy in the event of an impact between an errant vehicle and a second, typically stationary or slow-moving vehicle, in the hope of minimizing injury to the occupants of both vehicles, and, more specifically, to truck-mounted crash attenuators.
2. Description of the Related Art
Truck mounted attenuators (TMA""s) have been in use for many years. TMA""s typically comprise a fixed backup mounted to a dump truck or other vehicle and an energy absorbing cartridge attached to the fixed backup. In some TMA""s, the cartridge is attached to the fixed backup via a hinge to allow for rotation of the cartridge to a vertical orientation for transport. The TMA cartridge absorbs the impact of an errant vehicle that collides with it, thereby protecting the truck, the vehicle, and the occupants of both.
One important purpose for the TMA""s deployed on trucks and other vehicles, typically those used in highway construction, is for protecting workers in those vehicles. The trucks equipped with TMA""s are referred to as shadow vehicles, barrier vehicles, and advance warning vehicles. Shadow vehicles are moving trucks that effectively block errant vehicles in the flow of traffic from striking the workers directly ahead of the truck. The protected workers typically perform mobile activities, such as crack pouring, patching utility work, striping, coning, pavement repair, pavement marking, and delineator repair, and the shadow vehicle moves with and behind the workers. Barrier vehicles are effectively used to protect vehicles in the flow of traffic from a hazardous situation, such as blocking open excavations. The barrier vehicles may be unoccupied. Advance warning vehicles may be used to warn the drivers in the flow of traffic of an upcoming moving or stationary situation. An example of an advance warning vehicle is a truck in a lane of a highway displaying an arrow indicating that the lane is closed ahead and that vehicles in the lane need to start to merge into another lane.
A TMA functions by attempting to decelerate a vehicle that collides with it as safely as possible. Some TMA""s have been demonstrated to safely decelerate vehicles traveling up to 100 km/hr. To accomplish the deceleration, a typical prior art TMA is relatively long (approximately 12 to 15 feet). Such a length makes it no longer practical to rotate an entire cartridge that is directly attached to the fixed backup due to excessive height.
Some TMA""s have a fixed section or a strut attached to the fixed backup and the cartridge is rotatably mounted to the strut. The strut/cartridge configuration reduces the height of the vertically positioned cartridge, but the configuration extends quite far back from the rear of the truck. Because prior art TMA""s employ The wind resistance of the cartridge tends to create buffeting problems, which can make driving hazardous.
The present invention overcomes the problems of the prior art, namely excessive length during use in a horizontal position, and excessive height in a vertical transport position, as well as wind resistance and buffeting at highway speeds, and limited protection for errant vehicles which impact the TMA device from an angle (i.e. xe2x80x9ccoffin cornerxe2x80x9d impact).
Other advantages of the inventive system include its simple, low cost construction, as well as its modular construction, so that only damaged portions of the TMA can be removed and replaced in the field after impact.
The inventive system utilizes a novel method of buckling outwardly curved tubular members which comprise each member of the TMA system; i.e. the strut member and the cartridge member. The rigid sides of the cartridge are buckled at a high initial force, then proceed to crush at a lower force once the sides have buckled outwardly sufficiently to protect vehicle occupants during the critical first two feet of travel after impact. The goal is to prevent the vehicle from decelerating at a rate of more than 40 ft/sec. during this critical two feet of travel.